The present invention relates to a silicone rubber composition, and more particularly relates to a silicone rubber composition with excellent adhesion to organic resins even after being cured at a relatively low temperature, and even more particularly relates to a silicone rubber composition that is favorable for use in composite molding, whose adhesion to organic resins and mold release properties are excellent in composite molding, such as insert molding or multi-color molding, of an organic resin and a silicone rubber composition.
A method that has been adopted for bonding a silicone rubber to an organic resin in composite molding such as insert molding or multi-color molding involves priming a pre-molded organic resin and then curing it while it is brought together with a silicone rubber composition. A problem with this method, however, is that a priming step is required, and the adhesion of the silicone rubber decreases if this priming treatment is inadequate. Another problem is that the silicone rubber composition has to be cured at a relatively high temperature in order for this composition to adhere sufficiently to an organic resin, so organic resins with low heat resistance can not be used.
In addition, to bond a silicone rubber securely to an organic resin, there are known methods involving the use of an organic resin containing aliphatic unsaturated groups (Japanese Laid-Open Patent Applications 6-171021, 6-171022, and 6-171023), and methods featuring the use of a silicone rubber composition to which vinyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-methacryloxypropyl-trimethoxysilane, or another such adhesion improver has been added. A limitation to the former method, however, was that a special organic resin had to be used, while a problem with the latter method was that the mold release properties decreased, and in extreme cases, the silicone rubber even adhered to the mold.
The inventors arrived at the present invention as a result of diligent study aimed at solving the above problems. Specifically, it is an object of the present invention to provide a silicone rubber composition with excellent adhesion to organic resins even after being cured at a relatively low temperature, and in turn a silicone rubber composition that is favorable for use in composite molding, whose adhesion to organic resins and mold release properties are excellent in composite molding, such as insert molding or multi-color molding, of an organic resin and a silicone rubber composition.